LeetCode

Problem Statement

Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive).

The binary search tree is guaranteed to have unique values.

Example 1:

Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
Output: 32

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
Output: 23

Solution

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func rangeSumBST(root *TreeNode, L int, R int) int {
	return dfs(root, L, R)
}

func dfs(root *TreeNode, L int, R int) int {
	if root == nil {
		return 0
	}

	if root.Val >= L && root.Val <= R {
		return root.Val + dfs(root.Left, L, R) + dfs(root.Right, L, R)
	}

	return dfs(root.Left, L, R) + dfs(root.Right, L, R)
}